The present invention relates generally to medical devices, systems and methods, and more particularly to small, low cost, portable infusion devices and methods that are useable to achieve precise, sophisticated, and programmable flow patterns for the delivery of therapeutic liquids such as insulin to a mammalian patient. Even more particularly, the present invention is directed to a fluid flow sensor assembly for an infusion device and a method of determining fluid flow in an infusion device.
Today, there are numerous diseases and other physical ailments that are treated by various medicines including pharmaceuticals, nutritional formulas, biologically derived or active agents, hormonal and gene based material and other substances in both solid or liquid form. In the delivery of these medicines, it is often desirable to bypass the digestive system of a mammalian patient to avoid degradation of the active ingredients caused by the catalytic enzymes in the digestive tract and liver. Delivery of a medicine other than by way of the intestines is known as parenteral delivery. Parenteral delivery of various drugs in liquid form is often desired to enhance the effect of the substance being delivered, insuring that the unaltered medicine reaches its intended site at a significant concentration. Also, undesired side effects associated with other routes of delivery, such as systemic toxicity, can potentially be avoided.
Often, a medicine may only be available in a liquid form, or the liquid version may have desirable characteristics that cannot be achieved with solid or pill form. Delivery of liquid medicines may best be accomplished by infusing directly into the cardiovascular system via veins or arteries, into the subcutaneous tissue or directly into organs, tumors, cavities, bones or other site specific locations within the body.
Parenteral delivery of liquid medicines into the body is often accomplished by administering bolus injections using a needle and reservoir, or continuously by gravity driven dispensers or transdermal patch technologies. Bolus injections often imperfectly match the clinical needs of the patient, and usually require larger individual doses than are desired at the specific time they are given. Continuous delivery of medicine through gravity feed systems compromise the patient""s mobility and lifestyle, and limit the therapy to simplistic flow rates and profiles. Transdernal patches have special requirements of the medicine being delivered, particularly as it relates to the molecular structure, and similar to gravity feed systems, the control of the drug administration is severely limited.
Ambulatory infusion pumps have been developed for delivering liquid medicaments to a patient. These infusion devices have the ability to offer sophisticated fluid delivery profiles accomplishing bolus requirements, continuous infusion and variable flow rate delivery. These infusion capabilities usually result in better efficacy of the drug and therapy and less toxicity to the patient""s system. An example of a use of an ambulatory infusion pump is for the delivery of insulin for the treatment of diabetes mellitus. These pumps can deliver insulin on a continuous basal basis as well as a bolus basis as is disclosed in U.S. Pat. No. 4,498,843 to Schneider et al.
The ambulatory pumps often work with a reservoir to contain the liquid medicine, such as a cartridge, a syringe or an IV bag, and use electro-mechanical pumping or metering technology to deliver the medication to the patient via tubing from the infusion device to a needle that is inserted transcutaneously, or through the skin of the patient. The devices allow control and programming via electromechanical buttons or switches located on the housing of the device, and accessed by the patient or clinician. The devices include visual feedback via text or graphic screens, such as liquid crystal displays known as LCD""s, and may include alert or warning lights and audio or vibration signals and alarms. The device can be worn in a harness or pocket or strapped to the body of the patient.
Currently available ambulatory infusion devices are expensive, difficult to program and prepare for infusion, and tend to be bulky, heavy and very fragile. Filling these devices can be difficult and require the patient to carry both the intended medication as well as filling accessories. The devices require specialized care, maintenance, and cleaning to assure proper functionality and safety for their intended long term use. Due to the high cost of existing devices, healthcare providers limit the patient populations approved to use the devices and therapies for which the devices can be used.
Clearly, therefore, there was a need for a programmable and adjustable infusion system that is precise and reliable and can offer clinicians and patients a small, low cost, lightweight, easy-to-use alternative for parenteral delivery of liquid medicines.
In response, the applicant of the present application provided a small, low cost, light-weight, easy-to-use device for delivering liquid medicines to a patient. The device, which is described in detail in co-pending U.S. application Ser. No. 09/943,992, filed on Aug. 31, 2001, includes an exit port, a dispenser for causing fluid from a reservoir to flow to the exit port, a local processor programmed to cause a flow of fluid to the exit port based on flow instructions from a separate, remote control device, and a wireless receiver connected to the local processor for receiving the flow instructions. To reduce the size, complexity and costs of the device, the device is provided with a housing that is free of user input components, such as a keypad, for providing flow instructions to the local processor.
Such devices for delivering liquid medicines to a patient, however, are preferably monitored during operation to ensure the maximum benefit to the patient and to ensure the patient""s safety. In particular, ensuring the proper and intended flow of fluid from such a device is important. For example, the delivery of the liquid medicine should not be interrupted by a blockage in the flow path or tubing, i.e., occlusion, that delivers the liquid medicine to the patient. An occlusion may interfere with the accurate administration of the liquid medicine to the patient, and should be prevented or detected. Monitoring a fluid delivery device for occlusions during operation, therefore, is preferred.
What is still desired are new and improved devices for delivering fluid to a patient. Preferably, the fluid delivery devices will be simple in design, and inexpensive and easy to manufacture, in order to further reduce the size, complexity and costs of the devices, such that the devices lend themselves to being small and disposable in nature. In addition, the fluid delivery device will preferably include a flow condition sensor assembly for monitoring the delivery of fluid to a patient, and for ensuring that unwanted flow conditions such as occlusions or an empty fluid reservoir, are quickly detected.
The present invention provides a device for delivering fluid, such as insulin for example, to a patient. The device includes an exit port assembly adapted to connect to a transcutaneous patient access tool, a flow path extending from the exit port assembly, and a flow condition sensor assembly. The sensor assembly includes a resilient diaphragm having opposing first and second surfaces, with the first surface positioned against the flow path, a chamber wall positioned adjacent the second surface of the diaphragm and defining a sensor chamber against the second surface of the diaphragm, and at least one sensor arranged to provide a threshold signal when the second surface of the diaphragm expands into the chamber in response to at least one predetermined fluid flow condition occurring in the flow path. A sensor assembly constructed in accordance with the present invention, therefore, allows at least one predetermined fluid flow condition, such as an occlusion for example, to be detected within the flow path during operation of the fluid flow device.
According to one aspect of the present invention, the predetermined fluid flow condition is one of an occlusion in the flow path, a low flow of fluid in the flow path, a high flow of fluid in the flow path, and a desired flow of fluid in the flow path. According to another aspect, the chamber has a predetermined volume. According to a further aspect, the diaphragm comprises a thin, flat piece of flexible and resilient material.
According to an additional aspect of the present invention, the sensor is responsive to one of contact, pressure, light, magnetic strength, strain, and density. According to one aspect, the sensor includes a switch positioned within the chamber such that the second surface of the diaphragm closes the switch upon expanding into the chamber in response to the predetermined fluid flow condition within the flow path. According to a further aspect, the sensor includes a circuit having a lead positioned on the second surface of the diaphragm and a lead positioned on the chamber wall such that the leads come together and close the circuit when the second surface of the diaphragm expands into the chamber in response to the predetermined fluid flow condition. According to another aspect, the circuit includes multiple leads positioned on the chamber wall for determining multiple predetermined fluid flow conditions upon the lead on the diaphragm contacting each of the leads on the chamber wall.
According to still another aspect of the present invention, the flow condition sensor assembly includes an alarm connected to the sensor. According to one aspect, the alarm is adapted to be activated upon the sensor providing the threshold signal.
According to yet another aspect of the present invention, a processor is connected to the sensor of the sensor assembly, an alarm is connected to the processor, and the processor is programmed to activate the alarm upon receiving the threshold signal from the sensor. According to a further aspect, the processor is programmed to activate the alarm upon receiving the threshold signal from the sensor for more than a predetermined period. According to another aspect, the processor is programmed to activate the alarm upon receiving the threshold signal from the sensor for less than a predetermined period.
According to a further aspect of the present invention, a processor is connected to the sensor of the sensor assembly, and the processor is programmed to provide a signal indicative of an undesired flow condition upon receiving the threshold signal from the sensor. According to a further aspect, the processor is programmed to provide a signal indicative of an occluded flow condition upon receiving the threshold signal from the sensor for more than a predetermined period. According to another aspect, the processor is programmed to provide a signal indicative of a low flow condition upon receiving the threshold signal from the sensor for less than a predetermined period.
According to yet another aspect of the present invention, the sensor assembly includes multiple sensor chambers positioned against the second surface of the diaphragm. According to another aspect, the sensor assembly includes at least one of the sensors in each chamber. According to an additional aspect, each of the sensor chambers of the sensor assembly has a predetermined volume. According to a further aspect, the predetermined volumes are unequal.
These aspects of the invention together with additional features and advantages thereof may best be understood by reference to the following detailed descriptions and examples taken in connection with the accompanying illustrated drawings.